diff --git a/core/src/main/java/org/apache/calcite/sql/type/BasicSqlType.java b/core/src/main/java/org/apache/calcite/sql/type/BasicSqlType.java
index e8e9332d6197..635c07c662d3 100644
--- a/core/src/main/java/org/apache/calcite/sql/type/BasicSqlType.java
+++ b/core/src/main/java/org/apache/calcite/sql/type/BasicSqlType.java
@@ -205,6 +205,13 @@ BasicSqlType createWithCharsetAndCollation(Charset charset,
         sb.append(getScale());
       }
       sb.append(')');
+    } else if (printScale && typeName == SqlTypeName.DECIMAL) {
+      // Include scale in the digest when precision is not specified (CALCITE-5212).
+      sb.append('(');
+      sb.append(PRECISION_NOT_SPECIFIED);
+      sb.append(", ");
+      sb.append(scale);
+      sb.append(')');
     }
     if (!withDetail) {
       return;
diff --git a/core/src/test/java/org/apache/calcite/sql/type/SqlTypeFactoryTest.java b/core/src/test/java/org/apache/calcite/sql/type/SqlTypeFactoryTest.java
index 8f5e5e4018db..cab5de8f68f8 100644
--- a/core/src/test/java/org/apache/calcite/sql/type/SqlTypeFactoryTest.java
+++ b/core/src/test/java/org/apache/calcite/sql/type/SqlTypeFactoryTest.java
@@ -19,6 +19,7 @@
 import org.apache.calcite.rel.type.RelDataTypeFactory;
 import org.apache.calcite.rel.type.RelDataTypeField;
 import org.apache.calcite.rel.type.RelDataTypeFieldImpl;
+import org.apache.calcite.rel.type.RelDataTypeSystem;
 import org.apache.calcite.rel.type.RelRecordType;
 import org.apache.calcite.rel.type.StructKind;
 
@@ -35,7 +36,9 @@
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.hasToString;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -239,6 +242,27 @@ private void checkPrecision(int p0, int p1, int expectedMax,
     assertThat(SqlTypeUtil.comparePrecision(p1, p1), is(0));
   }
 
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-5212">[CALCITE-5212]
+   * Decimal with scale but unspecified precision collides in type cache</a>. */
+  @Test void testCreateSqlTypeDecimalUnspecifiedPrecisionWithScale() {
+    SqlTypeFixture f = new SqlTypeFixture();
+    RelDataTypeFactory tf = f.typeFactory;
+    final int pUn = RelDataType.PRECISION_NOT_SPECIFIED;
+    RelDataType d5 = tf.createSqlType(SqlTypeName.DECIMAL, pUn, 5);
+    RelDataType d3 = tf.createSqlType(SqlTypeName.DECIMAL, pUn, 3);
+    assertEquals(5, d5.getScale());
+    assertEquals(3, d3.getScale());
+    assertNotEquals(d5, d3);
+    assertNotEquals(d5.getFullTypeString(), d3.getFullTypeString());
+    // Order independence: first created shape must not be returned for another scale.
+    SqlTypeFactoryImpl tf2 = new SqlTypeFactoryImpl(RelDataTypeSystem.DEFAULT);
+    RelDataType d3b = tf2.createSqlType(SqlTypeName.DECIMAL, pUn, 3);
+    RelDataType d5b = tf2.createSqlType(SqlTypeName.DECIMAL, pUn, 5);
+    assertEquals(3, d3b.getScale());
+    assertEquals(5, d5b.getScale());
+  }
+
   /** Test case for
    * <a href="https://issues.apache.org/jira/browse/CALCITE-2464">[CALCITE-2464]
    * Allow to set nullability for columns of structured types</a>. */